The disclosure of Japanese Patent Application No. 2001-173328 filed on Jun. 8, 2001, including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of Invention
The invention relates to an apparatus and method for detecting a change of a neutral position of a valve of an electromagnetic valve actuation system which is caused by e.g., aging of the electromagnetic valve actuation system, and an apparatus and method for controlling the valve. The electromagnetic valve actuation system to which the invention drives a valve such that the valve is placed in an open position and a closed position by an electromagnetic force of an electromagnet, and the valve is urged to a neutral position by urging forces of urging members for urging the valve in the valve-opening and valve-closing directions. The neutral position is a position where the urging forces are balanced.
2. Description of Related Art
For drive control of the electromagnetic valve actuation system, not only is assuring operation stability of the electromagnetic valve actuation system important, but also minimizing power consumption and suppressing noise generated by opening and closing the valve are also important in terms of the performance of the electromagnetic valve actuation system. Therefore, various efforts have been made to satisfy the above requirements. For example, a current is supplied to the electromagnet according to a current supply pattern that is preset so that the requirements can be satisfied.
However, if the neutral position is changed due to aging and the like, drive control of the electromagnetic valve actuation system (such as the current supply pattern to the electromagnet) becomes inappropriate. For example, an insufficient electromagnetic force would degrade the ability to reliably hold the valve at the full-closed position or full-open position, and excessive electromagnetic force would increase the noise generated when the valve is seated on a valve seat.
In view of the above problems, for example, Japanese Patent Laid-Open Publication No. 2000-8894 proposes detecting the change of the neutral position of the valve based on a lifted position when the electromagnet does not generate the electromagnetic force and the valve stands still at the neutral position, and correcting the current supply pattern based on the detection result.
In the case of an electromagnetic valve actuation system whose valve may stand still at the neutral position, it is possible to detect the change of the neutral position by the method described in the above publication. As described in Japanese Patent Laid-Open Publication No. 2000-161032, however, some electromagnetic valve actuation systems have a valve which does not stand still at the neutral position and is held at the open position or closed position even when the engine is stopped. In such an electromagnetic valve actuation system, the change of the neutral position cannot be known by the aforementioned method. Therefore, the above detecting method is still problematic in view of versatility.
The invention thus accurately detects a change of a neutral position of a valve in an electromagnetic valve actuation system having a valve that does not stand still at the neutral position. Also the invention also provides control of the valve based on the result of the detection.
A first aspect of the invention relates to an apparatus for detecting a change of a neutral position of a valve of an electromagnetic valve actuation system. In the first aspect of the invention, the apparatus for detecting the change of the neutral position is applied to the electromagnetic valve actuation system having the valve that is urged to the neutral position by urging forces of urging members for urging the valve in valve-opening and valve-closing directions. The neutral position is a position where the urging forces are balanced. The apparatus includes an electromagnet that drives the valve in the valve-opening and the valve-closing directions by an electromagnetic force and a controller that releases the valve held at one of a first terminal position in a closed position side and a second terminal position in an open position side, e.g., a full-closed position or a full-open position, and then attracts the valve to one of the terminal positions by supplying a current to the electromagnet, and that detects the change of the neutral position based on a parameter that represents a displacement pattern of the valve obtained by displacing the valve.
In the above structure, the valve, which is held at one of the first terminal position and the second terminal position, e.g., the full-closed position or the full-open position, is released and then attracted to one of the terminal positions by supplying the current to the electromagnet. The change of the neutral position is detected based on the parameter that represents the displacement pattern of the valve obtained by displacing the valve. The above structure thus enables implementation of a versatile apparatus that is capable of detecting the change of the neutral position of the valve of the electromagnetic valve actuation system even when the valve does not stand still at the neutral position. The displacement pattern of the valve changes depending on whether the neutral position is changed. Therefore, the change of the neutral position can be detected by measuring the parameter representing the displacement pattern of the valve.
A second aspect of the invention relates to a method for detecting a change of a neutral position of a valve of an electromagnetic valve actuation system. The method includes a first step of releasing the valve held at one of a first terminal position in a closed position side and a second terminal position in an open position side, and then attracting the valve to one of the terminal positions by supplying a current to an electromagnet of the electromagnetic valve actuation system, a second step of measuring a parameter that represents a displacement pattern of the valve obtained by displacement of the valve; and a third step of detecting the change of the neutral position based on the measured parameter in the second step.